Magnitude 6.1 quake shakes Mexico

(CNN) -- A magnitude 6.1 earthquake struck the state of Chiapas in southern Mexico Thursday evening, the U.S. Geological Survey reported.

There was no immediate information on damage or casualties from the quake, which was felt in Mexico City at about 8:09 p.m. (1:09 a.m. GMT).

But the director of the Mexican National Seismological Service said the quake was very deep -- some 77.6 miles below the Earth's surface, according to the USGS -- and was not expected to cause damage on the surface. Earthquakes centered closer to the Earth's surface produce stronger shaking and generally can cause more damage than those further underground.

The quake's epicenter was about 10 miles southwest of the town of Ocozococautla, the USGS said, and about 25 miles west-southwest of Tuxtla Gutierrez.

Thousands of residents of Tuxtla Gutierrez ran out of homes and buildings as the ground trembled and windows rattled, according to reports from The Associated Press. Electricity for much of the city was also cut off for several minutes, AP reported.

Chiapas residents told CNN their homes were not damaged. However, there are very poor and remote areas in the state that will need to be surveyed for damage. E-mail to a friend

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